My experience is if your customer has used THAT card at another vendor using Square and they requested an email receipt there, then Square automatically sends an email receipt from then on from any other vendor. I have purchased from a vendor using Square and my card does the same thing. At the bottom of the receipt, in the fine print of course, is a statement from Square that the customer can choose to opt out. I tell my customers about this and they seem to be fine with it, saves them from having to reenter their info every time.
